Biogas as an environmentally friendly energy source is becoming increasingly valuable. This can be seen by the growing number of biogas powered vehicles. Though biogas production has been around for a long time, there are still a lot of challenges when it comes to efficient large-scale biogas production. During my semester abroad in Norway, I have been working on biogas production by anaerobic digestion, and I want to give a brief overview of our experiments and their outcomes.
Anaerobic Digestion
Anaerobic digestion (AD) is a process by which organic waste material is broken down by naturally occuring bacteria in the absence of oxygen. Whereby the name ‘anaerobic’, in contrast to ‘aerobic’, refers to the absence of oxygen. Organic waste material on the other hand is the technical term for plant and animal material like food waste, manure, sewage and energy crops. While AD occurs naturally as well, it can also be facilitated in a controlled environment like a biogas production facility, also called a Anaerobic Digester. You can find Anaerobic Digesters on many farms, which enables farmers to directly make use of their organic waste material. AD results in two main products, biogas and digestate. The digestate is more of a by-product. It is used to fertilize crops which in their turn can be used as fuel for the AD process again. It therefore resembles a closed loop. The biogas on the other hand can be either transported and used directly in its gaseous form or it can be burned in a CHP unit.
Experiments
In our biogas lab project we investigated different kinds of food, the technical term is substrate, and their impact on biogas production rates. One sample plot is shown in Fig. 2. For this specific sample, apple juice (carbohydrates) and cream (fat) were fed to the microorganisms, resulting in a strong initial peak in biogas production (on run 1 (R1)). This graph also shows the results in a second run (R2), where another dose of substrate was introduced into the biogas reactor. It can be seen, that there is a long delay between the introduction of the substrate and the release of biogas.
Challenges
This is just one example of several studies, which show the difficulties with anaerobic digestion. Because the process of anaerobic digestion consists of many biological suprocesses running in parallel, their are a lot of factors that need to be considered. Therefore, the experiments were complimented with simulations in Aquasim. In our research project we were able to get a good overview of the representational capabilities of a state-of-the-art simulation framework and explore the challenges that novel simulation algorithms face.
If you want to know more, feel free to contact me.